外文翻译---一种新型的液压锻造操作机的智能控制-液压系统(编辑修改稿)

外文翻译---一种新型的液压锻造操作机的智能控制-液压系统(编辑修改稿)内容摘要：

e relief valve in damping hydraulic circuit. The reaction force in horizontal direction almost keeps constant that depends on the property of the relief valve. 4. Pressure/Position Control Method of Hydraulic Servosystem A block diagram of the overall control scheme is shown in Figure3. The system is posed of controller, power amplifier, servovalve, cylinder, pressure sensor, and position sensor. Figure 3: Block diagram of hybrid pressure/position control system. Hybrid pressure/position control is very useful in manipulator lifting control where plunger cylinders are used. Based on this method, the intelligent control of forging manipulator is realized. 5. Analysis of Intelligent Control . Automatic Identification of Pressure Value Settings As shown in Figure 4, when the workpiece is grasped by the manipulator, the hybrid pressure/position control method is used, and the pressure and position mand values are set with original ones of P0 and X0. The workpiece is lifted up with a constant force created by hybrid control loop with mand pressure P0. When the position mand value X0 is exceeded, the negative position error feeds back to the pressure control loop, the actual pressure in system begins to decrease and will stop decreasing at the weight balance pressure. In equilibrium, the workpiece stops moving, and the actual lifting force equals the total weight of the workpiece, gripper, and its support. Record this actual balance pressure and use it as the pressure value settings in pliance control in forging process. Figure 4: Illustration of the measurement of workpiece. . Automatic Identification of the Placement Height of Workpiece As shown in Figure 5, supposing the workpiece is staying at a position with equilibrium of forces, decrease the mand position X0 in a constant rate, then the balance has been broken. For the feedback of error of position increasing, the actual pressure will bee smaller and try to go to another equilibrium state. The actual lifting force is less than the weight of the workpiece, gripper, and its support now. So the workpiece moves down until touching the lower die. At this moment, the actual pressure drops rapidly. According to the change rate of pressure, the workpiece placement state can be identified automatically. Keep the mand position X0 with the height value of workpiece position placed on the lower die. The pressure and position of lifting cylinders goes to a new balance. Figure5: Illustration of the placement of workpiece. . Compliance in Vertical Direction and Move Up Automatically As shown in Figure 6, when the workpiece is pressed by the upper die, the load on cylinder will increase for the deformation of workpiece。 this process is called “ inpress.” In the mode of pressure/position control, the increased load makes the workpiece move down, and when X X0, the position error feed back does not work. During this period, the force acting on the workpiece by manipulator increases from weight balance pressure to the mand pressure P0, while it is still much smaller than the press force. Thus, the pliance in vertical direction is realized. When press is finished and upper die moves up, this process is called “ afterpress,” the load on cylinder decreases. The lifting force makes the workpiece move up until the pressure and position of lifting cylinders goes to a new balance. Figure 6: Illustration of the pliance during forging steps. 6. Experiment Results The experiments were executed on a real prototype of the novel hydraulic forging manipulator in our institute, as shown in Figure 7. The mechanism and hydraulic system of the manipulator is identical with a railbound forging manipulator with a carrying capacity of 2020 kN and 4000 kNm load moment which is designed by our institute. The main characteristics of this prototype are carrying capacity 60 kN, load moment 150 kNm, and installed power 130 kW. The hydraulic actuators are supplied by a constant pressure pump source and controlled by servoproportional valves with position transducer. A programmable logic controller performs all control actions. Figure 7: Prototype of the novel hydraulic forging manipulator. Figure 8 demonstrates the measurement of the weight and the gravitational torque of workpiece. The controller attempts to maintain a constant pressure  MPa, and while the height of the workpiece position exceeds the preset mand position 400 mm, the negative feedback of position works. When lifting cylinders stop moving, control returns to a stable steady state. The weightbalanced pressure can be identified from the curve, which is  MPa Figure 8: Pressure curve in lifting cylinder. Figure 9 depicts the p。